NIEHS is carrying out a long term study looking at the potential health effects of the Deepwater Horizon oil spill in various responder populations. During FY 2017, the GuLF STUDY (Gulf Long-term Follow-Up Study) completed follow-up interviews with participants (approximately 2 years after they enrolled), with a response rate of nearly 70%. Deaths through 2014 were identified through linkage with the National Death Index. Additionally, 3,403 English-speaking cohort members living within 60 miles of clinics in New Orleans, LA or Mobile, AL completed clinical examinations. Participants underwent comprehensive lung function testing, completed a battery of behavioral and physiological tests to assess neurological function, and provided blood, urine, and saliva samples for further study. Biological samples were collected to assess immune, renal, and kidney function and to allow for longitudinal comparisons for the subset of persons who provided samples at an earlier home visit and at the clinic. Smaller clinical sub-studies, such as assessing temporal changes in stress hormones through collection of repeat saliva samples, were also included. Finally, participants completed a comprehensive clinical mental health assessment which included questionnaire modules to assess traumatic events and substance abuse as well as questions designed to assess mental health services utilization by participants. Planning for a second follow-up interview has begun with the goal of launching in FY2018. NIEHS investigators are continuing efforts to evaluate all of the available environmental and occupational exposure monitoring data in order to more completely characterize exposures in the study population. An ordinal job-exposure matrix was developed that characterizes exposure to total hydrocarbons as a marker for oil spill experiences. Questionnaire data were used to characterize exposure to toxicants associated with burning oil and to dispersants. Several foundational manuscripts are in press and preliminary exposure-outcome papers using these exposure metrics and data self-reported at the enrollment telephone interview have been submitted for publication. Ongoing statistical modeling will lead to the development of chemical specific, time dependent job-exposure metrics, e.g. for the BTEX chemicals and other exposures related to oil spill cleanup. Spatial models are being developed to account for exposure to PM2.5 and dispersants, and to account for small-area neighborhood features such as socioeconomic factors or crime statistics within a county or at the census tract level. Approaches and preliminary results from exposure characterization efforts were presented at national and international meetings and workshops. Ongoing analysis of baseline data is focusing on mental health, pulmonary function, cardiovascular outcomes, respiratory health and a range of specific and non-specific symptoms reported by participants while working on the response and clean-up. A paper describing the cohort and methods used has been published. A paper describing the GuLF STUDY biorepository and how to access samples has also been published and a paper describing the ordinal exposure metrics is in press. Published papers also describe statistical methods used in developing exposure measures for participants based on environmental sampling data from the time of the spill and questionnaire responses; plans have been made to publish a monograph of papers with on additional exposure assessment metrics (e.g. dermal exposures) and statistical development. Published papers have described how physical health symptoms and socioeconomic factors contribute to workers risk for mental health symptoms and how ambient exposure to volatile organic compounds such as benzene may be associated with hematologic effects such as decreased hemoglobin concentration. A paper in press describes acute effects in workers with likely exposure to dispersants; this is the first report of human health effects associated with these chemicals. Finally, papers describing the lessons learned from the experience of launching the GuLF STUDY and how it can serve as a model for future disaster research such as the NIH Disaster Research Response program were published.